Efforts to slow the spread of HIV among drug-using populations have focused on intravenous drug users(IDU), despite the strong link between the non-injection use of stimulants, such as methamphetamine (meth), and high risk sex. The overall objective of this proposal is to evaluate the effectiveness of a chronic treatment model of sexual risk reduction for HIV-negative, "heterosexually-identified" meth users (non-IDU) whose high risk sexual practices put them "at risk" for contracting HIV/STDs. Because few studies have shown the long-term benefits of short-term interventions, our study will examine whether variables responsible for behavior acquisition differ from variables responsible for behavior maintenance. Our intervention integrates a clinical approach (i.e., motivational interviewing) with theory-based principles of behavior change (i.e., Social Cognitive Theory & Theory of Reasoned Action). Three major questions will be addressed: 1) Can non-gay "at risk" meth users modify their high risk sexual practices?; 2) Do safer sex maintenance sessions result in longer-term treatment effects?; and 3) Do the underlying mechanisms of behavior change and behavior maintenance differ? We have piloted our 8-session intervention counseling program with eight participants. We have also completed 26 survey questionnaires and 10 qualitative interviews, accessed government data and public records on meth use in San Diego County, and consulted with community leaders and organizations to identify recruitment areas and sources. These "local" pilot data have also helped us to refine our intervention materials to ensure cultural sensitivity and responsiveness to gender-based issues. In the proposed 5 year study, 450 "heterosexually- identified" men and women who are regular users of meth and who have had unprotected sex at least once during the previous two months will be randomly assigned to one of three conditions: 1) a " safer sex maintenance (MT) program" (i.e., 4-90 min. sessions, MT sessions (@, 7, 8, 9, and 10 months post-counseling); 2) a "no maintenance" safer sex counseling program (i.e., 4-90 minute sessions); and 3) a "diet and exercise" control condition (time equivalent with MT program). Printed materials on risk factors and safer sex will be distributed to controls at baseline. Followup assessments for all subjects will be conducted at 6, 12, and 18 months post-baseline assessment. A variety of outcomes will be examined (e.g., unprotected vaginal, anal, oral sex; number of STDs, partner types). Subgroup differences in the effectiveness of the intervention based on individual factors (e.g.,ethnicity, gender) and psychosocial factors (e.g., readiness for change) will be explored.